Foam-filled caps for sealing inkjet printheads

ABSTRACT

A foam-filled cap sealing ink-ejecting nozzles of an inkjet printhead in a printing mechanism has a two-layer structure, with an outer skin layer of an elastomer, and a second foam core layer inside the skin. The skin defines a sealing lip that surrounds the nozzles when the cap is in a sealing position to avoid unnecessary drying of the ink. The skin has an interior surface that defines a cavity under the sealing lip. The foam core, located within the cavity, may be formed by expanding a foam preform or by injecting raw foam into the cavity. An insert may be molded into the cap structure for use in mounting the cap in the printing mechanism. An optional backing layer molded to the structure is used to attach a vent basin to the cap. A method of constructing this cap, and a printing mechanism having this cap, are also described.

RELATED APPLICATION

This is a continuation-in-part application of the co-pending U.S. patentapplication Ser. No. 08/808,366, filed on Feb. 28, 1997 now U.S. Pat.No. 5,956,053, which is a continuation-in-part application of theco-pending U.S. patent application Ser. No. 08/741,850, filed on Oct.31, 1996 now U.S. Pat. No. 5,936,647, all having at least oneco-inventor in common.

FIELD OF THE INVENTION

The present invention relates generally to inkjet printing mechanisms,and more particularly to a foam-filled cap for sealing an inkjetprinthead with an improved seal, particularly when sealing over surfaceirregularities on the printhead.

BACKGROUND OF THE INVENTION

Inkjet printing mechanisms use cartridges, often called “pens,” whicheject drops of liquid colorant, referred to generally herein as “ink,”onto a page. Each pen has a printhead formed with very small nozzlesthrough which the ink drops are fired. To print an image, the printheadis propelled back and forth across the page, ejecting drops of ink in adesired pattern as it moves. The particular ink ejection mechanismwithin the printhead may take on a variety of different forms known tothose skilled in the art, such as those using piezo-electric or thermalprinthead technology. For instance, two earlier thermal ink ejectionmechanisms are shown in U.S. Pat. Nos. 5,278,584 and 4,683,481. In athermal system, a barrier layer containing ink channels and vaporizationchambers is located between a nozzle orifice plate and a substratelayer. This substrate layer typically contains linear arrays of heaterelements, such as resistors, which are energized to heat ink within thevaporization chambers. Upon heating, an ink droplet is ejected from anozzle associated with the energized resistor. By selectively energizingthe resistors as the printhead moves across the page, the ink isexpelled in a pattern on the print media to form a desired image (e.g.,picture, chart or text).

To clean and protect the printhead, typically a “service station”mechanism is supported by the printer chassis so the printhead can bemoved over the station for maintenance. For storage, or duringnon-printing periods, these service stations usually include a cappingsystem which substantially seals the printhead nozzles from contaminantsand drying. Some caps are also designed to facilitate priming, such asby being connected to a pumping unit that draws a vacuum on theprinthead. During operation, clogs in the printhead are periodicallycleared by firing a number of drops of ink through each of the nozzlesin a process known as “spitting,” with the waste ink being collected ina “spittoon” reservoir portion of the service station. After spitting,uncapping, or occasionally during printing, most service stations havean elastomeric wiper that wipes the printhead surface to remove inkresidue, as well as any paper dust or other debris that has collected onthe printhead. The wiping action is usually achieved through relativemotion of the printhead and wiper, for instance by moving the printheadacross the wiper, by moving the wiper across the printhead, or by movingboth the printhead and the wiper.

To improve the clarity and contrast of the printed image, recentresearch has focused on improving the ink itself. To provide quicker,more waterfast printing with darker blacks and more vivid colors,pigment-based inks have been developed. These pigment-based inks have ahigher solid content than the earlier dye-based inks, which results in ahigher optical density for the new inks. Both types of ink dry quickly,which allows inkjet printing mechanisms to form high quality images onreadily available and economical plain paper.

Early inkjet printers used a single monochromatic pen, typicallycarrying black ink. Later generations of inkjet printing mechanisms useda black pen which was interchangeable with a tri-color pen, typicallyone carrying the colors of cyan, magenta and yellow within a singlecartridge. The tri-color pen printed a “process” or “composite” blackimage, by depositing drops of cyan, magenta, and yellow inks all at thesame location. Unfortunately, the composite black images usually hadrough edges, and a non-black hue or cast, depending for instance, uponthe type of paper used. The next generation of printers further enhancedthe images by using either a dual pen system or a quad pen system. Thedual pen printers had a black pen and a tri-color pen mounted in asingle carriage to print crisp, clear black text while providing fullcolor images.

The quad pen printing mechanisms had four separate pens that carriedblack ink, cyan ink, magenta ink, and yellow ink. Quad pen plotterstypically carried four pens in four separate carriages, so each penneeded individual servicing. Quad pen desktop printers were designed tocarry four cartridges in a single carriage, so all four cartridges couldbe serviced by a single service station. As the inkjet industryinvestigates new printhead designs, there is a trend toward usingpermanent or semi-permanent printheads in what is known in the industryas an “off-axis” printer. In an off-axis system, the printheads carryonly a small ink supply across the printzone, with this supply beingreplenished through tubing that delivers ink from an “off-axis”stationary reservoir placed at a remote location, typically inside adesktop printer, although large format plotters and industrialimplementations may store their ink supplies external to the printingmechanism. The smaller on-board ink supply makes these off-axis desktopprinters quite suitable for quad pen designs.

These earlier dual and quad pen printers required an elaborate cappingmechanism to hermetically seal each of the printheads during periods ofinactivity. A variety of different mechanisms have been used to move theservicing implements into engagement with respective printheads. Forexample, a dual printhead servicing mechanism which moves the caps in aperpendicular direction toward the orifice plates of the printheads isshown in U.S. Pat. No. 5,155,497, assigned to the present assignee,Hewlett-Packard Company, of Palo Alto, Calif. Another dual printheadservicing mechanism uses the carriage to pull the caps laterally up aramp and into contact with the printheads, as shown in U.S. Pat.5,440,331, also assigned to the Hewlett-Packard Company. A translationaldevice for capping dual inkjet printheads is commercially available inthe DeskJet® 720C model inkjet printer produced by the Hewlett-PackardCompany. A rotary device for capping dual inkjet printheads iscommercially available in several models of printers produced by theHewlett-Packard Company, including the DeskJet® 850C, 855C, 820C, 870Cand 890C model inkjet printers. Examples of a quad pen capping systemthat uses a translational motion are seen in several other commerciallyavailable printers produced by the Hewlett-Packard Company, includingthe DeskJet® 1200 and 1600 models. Thus, a variety of differentmechanisms and angles of approach may be used to physically move thecaps into engagement with the printheads.

The caps in these earlier service station mechanisms typically includedan elastomeric sealing lip supported by a movable platform or sled.Typically, provisions were made for venting the sealing cavity as thecap lips are brought into contact with the printhead. Without a ventingfeature, air could be forced into the printhead nozzles during capping,which could deprime the nozzles. A variety of capillary passagewayventing schemes are known to those skilled in the art, such as thoseshown in U.S. Pat. Nos. 5,027,134; 5,216,449; and 5,517,220, allassigned to the present assignee, the Hewlett-Packard Company.

The earlier cap sleds were often produced using high temperaturethermoplastic materials or thermoset plastic materials which allowed theelastomeric sealing lips to be onsert molded onto the sled. Theelastomeric sealing lips were sometimes joined at their base to form acup-like structure, whereas other cap lip designs projected upwardlyfrom the sled, with the sled itself forming the bottom portion of thesealing cavity. Unfortunately, the systems which used a portion of thesled to define the sealing cavity often had leaks where the cap lipsjoined the sled. To seal these leaks at the lip/sled interface, highercapping forces were used to physically push the elastomeric lip into atight seal with the sled. This solution was unfortunate because thesehigher capping forces may damage, unseat or misalign the printhead, orat the vary least require a more robust printhead design which isusually more costly.

Capping systems need to provide an adequate seal while accommodating aseveral different types of variations in the printhead. For example,today's printhead orifice plates often have a waviness or ripple totheir surface contour because commercially available orifice platesunfortunately are not perfectly planar. Besides waviness, these orificeplates may also be slightly bowed in a convex, concave or compound (bothconvex and concave) configuration. The waviness property may generate aheight variation of up to 0.05-0.08 millimeters (2-3 mils; 0.002-0.003inches). These orifice plates may also have some inherent surfaceroughness over which the cap must seal. The typical way of coping withboth the waviness problem and the surface roughness problem is throughelastomer compliance, where a soft material is used for the cap lips.The soft cap lips compress and conform to seal over these irregularitiesin the orifice plate. For instance, one earlier suspended lipconfiguration having a single upwardly projecting ridge for a sealinglip is shown in U.S. Pat. No. 5,448,270, assigned to the Hewlett-PackardCompany, the present assignee.

Another major surface irregularity over which some printhead caps mustseal are one or more encapsulant beads which are used to attach thesilicon nozzle plate to a portion of an electrical flex circuit whichdelivers firing signals to energize the printhead resistors. Anenergized resistor heats the ink until a droplet is ejected from thenozzle associated with the energized resistor. These encapsulant beadsproject beyond the outer surface of the nozzle plates. In the past, capswere designed to avoid sealing over the encapsulant bead regions, eitherby sealing between the beads or beyond them. One printer design, theDeskJet® 693C color inkjet printer sold by the Hewlett-Packard Companyof Palo Alto, Calif., has a capping system that accommodatesinterchangeable black and photo-quality color pens, either of which isused in combination with a standard tri-color pen. This capping systemused a multiple sealing lip system to seal across (perpendicular to) theencapsulant beads.

One other earlier capping system, is currently commercially available inthe DeskJet® 850C, 855C, 820C and 870C model color inkjet printers, soldby the Hewlett-Packard Company of Palo Alto, Calif. The capping systemin these earlier printers used a multiple sealing lip system to sealalong the length of the encapsulant beads. That is, in this earlierdesign the multiple sealing lips ran parallel to the encapsulant beadsto accommodate for manufacturing tolerance accumulation and/or capplacement tolerance, so at least one of the multiple lips would land ina suitable location on the orifice plate to form a seal. Unfortunately,these fine multiple lips are very difficult to manufacture, Often thelips break off as they are removed from the mold, so the scrap rate isrelatively high, which translates to a higher overall piece price forthe printer manufacture. Indeed, only a few companies are even capableof consistently producing quality caps of this multi-lip design.

Proper capping requires providing an adequate hermetic seal withoutapplying excessive force which may damage the delicate printheads orunseat the pens from their locating datums in the carriage. Moreover, itwould be desirable to provide such a capping system which is moreeconomical to manufacture than earlier capping systems, and which can bemanufactured by a variety of vendors.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a cap is provided forsealing ink-ejecting nozzles of an inkjet printhead in an inkjetprinting mechanism. The cap includes a skin layer of an elastomer havingan exterior surface and a interior surface, with the exterior surfacedefining a sealing lip to surround the ink-ejecting nozzles when saidcap is in a sealing position and to define a sealing chamber. Theinterior surface of the skin layer defines a cavity under at least aportion of the sealing lip. The cap also includes a foam core within thecavity.

According to another aspect of the present invention, a method isprovided of constructing a printhead cap for sealing ink-ejectingnozzles of an inkjet printhead in an inkjet printing mechanism. Themethod includes the steps of molding a skin layer of an elastomer havingan exterior surface and an interior surface, with the exterior surfacedefining a sealing lip to surround the ink-ejecting nozzles when saidcap is in a sealing position and to define a sealing chamber, with theinterior surface of the skin layer defining a cavity opposite at least aportion of the sealing lip. In a foaming step, an elastomer is foamedwithin the cavity to form a foam core in the cavity. According toanother aspect of the present invention, an inkjet printing mechanismmay be provided with a capping system as described above.

An overall goal of the present invention is to provide an inkjetprinting mechanism which prints sharp vivid images over the life of thepen and the printing mechanism, particularly when using fast dryingpigment or dye-based inks.

A further goal of the present invention is to provide a capping systemthat adequately seals inkjet printheads in an inkjet printing mechanism,with the capping system being easier to manufacture than earlier systemsto provide consumers with a robust, reliable and economical inkjetprinting unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one form of an inkjet printingmechanism, here, an off-axis inkjet printer, including a printheadservice station having a capping system of the present invention.

FIG. 2 is an enlarged front elevational sectional view of one form of acapping system of the present invention, shown supported by a sled andsealing four discrete inkjet printheads mounted in a single carriage.

FIG. 3 is a top plan view taken along line 3—3 of FIG. 2, with the sledomitted for clarity.

FIG. 4 is an enlarged perspective view of an alternate manner ofconstructing the capping system resent invention.

FIG. 5 is an enlarged, side elevational, sectional view of the cappingsystem of FIG. 4.

FIG. 6 is a top plan view of the support member upon which the cap ofFIG. 4 is onsert molded.

FIG. 7 is enlarged, side elevational, sectional view of the sealing lipportion of the capping system FIG. 4 shown sealing over an encapsulantbead of a printhead.

FIG. 8 is a bottom view of the capping system of FIG. 4, shown with thecatch basin removed.

FIG. 9 is a top plan view of the catch basin portion of the cappingsystem of FIG.4.

FIG. 10 is an enlarged, side elevational, sectional view taken alongline 10—10 of FIG. 9.

FIG. 11 is an enlarged perspective view of an alternate manner ofconstructing a cap, here a foam-filled cap for another form of thecapping system of the present invention.

FIG. 12 is a process diagram showing steps A, B, C and D to illustratedifferent manners of manufacturing the foam-filled cap body of FIG. 11.

FIG. 13 is a process diagram showing steps A, B, C and D to illustrateanother manner of manufacturing the foam-filled cap body of FIG. 11.

FIG.14 is a process diagram showing a final step which may be usedfollowing step D of FIG. 13 to form means for attaching the catch basinportion of the capping system to the foam-filled cap body of FIG. 11.

FIG. 15 is a process diagram showing a final step which may be usedfollowing step D of FIG. 12 to install an insert member, as well as toform means for attaching the catch basin portion of the capping systemto the foam-filled cap body of FIG. 11.

FIG. 16 is a process diagram showing steps A, B, C and D to illustratean additional manner of manufacturing the foam-filled cap body of FIG.11.

FIG. 17 is a fragmented, enlarged perspective view of an alternatemanner of constructing the capping system of the present invention,using a series of foam-filled cap bodies for sealing inkjet printheadswithin the printer of FIG. 1.

FIG. 18 is an enlarged, front elevational, sectional view taken alongline 18—18 of FIG. 17.

FIG. 19 is an enlarged perspective view of an alternate manner ofconstructing the capping system of the present invention, using a seriesof foam-filled cap bodies for sealing inkjet printheads within theprinter of FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 illustrates an embodiment of an inkjet printing mechanism, hereshown as an “off-axis” inkjet printer 20, constructed in accordance withthe present invention, which may be used for printing for businessreports, correspondence, desktop publishing, and the like, in anindustrial, office, home or other environment. A variety of inkjetprinting mechanisms are commercially available. For instance, some ofthe printing mechanisms that may embody the present invention includeplotters, portable printing units, copiers, cameras, video printers, andfacsimile machines, to name a few, as well as various combinationdevices, such as a combination facsimile/printer. For convenience theconcepts of the present invention are illustrated in the environment ofan inkjet printer 20.

While it is apparent that the printer components may vary from model tomodel, the typical inkjet printer 20 includes a frame or chassis 22surrounded by a housing, casing or enclosure 24, typically of a plasticmaterial. Sheets of print media are fed through a printzone 25 by amedia handling system 26. The print media may be any type of suitablesheet material, such as paper, card-stock, transparencies, photographicpaper, fabric, mylar, and the like, but for convenience, the illustratedembodiment is described using paper as the print medium. The mediahandling system 26 has a feed tray 28 for storing sheets of paper beforeprinting. A series of conventional paper drive rollers driven by astepper motor and drive gear assembly (not shown), may be used to movethe print media from the input supply tray 28, through the printzone 25,and after printing, onto a pair of extended output drying wing members30, shown in a retracted or rest position in FIG. 1. The wings 30momentarily hold a newly printed sheet above any previously printedsheets still drying in an output tray portion 32, then the wings 30retract to the sides to drop the newly printed sheet into the outputtray 32. The media handling system 26 may include a series of adjustmentmechanisms for accommodating different sizes of print media, includingletter, legal, A-4, envelopes, fan-folded banner paper, etc., such as asliding length adjustment lever 34, a sliding width adjustment lever 36,and an envelope feed port 38.

The printer 20 also has a printer controller, illustrated schematicallyas a microprocessor 40, that receives instructions from a host device,typically a computer, such as a personal computer (not shown) or a localarea network (“LAN”) system. The printer controller 40 may also operatein response to user inputs provided through a key pad 42 located on theexterior of the casing 24. A monitor coupled to the computer host may beused to display visual information to an operator, such as the printerstatus or a particular program being run on the host computer. Personalcomputers, their input devices, such as a keyboard and/or a mousedevice, and monitors are all well known to those skilled in the art.

A carriage guide rod 44 is supported by the chassis 22 to slideablysupport an off-axis inkjet pen carriage system 45 for travel back andforth across the printzone 25 along a scanning axis 46. The carriage 45is also propelled along guide rod 44 into a servicing region, asindicated generally by arrow 48, located within the interior of thehousing 24. A conventional carriage drive gear and DC (direct current)motor assembly may be coupled to drive an endless belt (not shown),which may be secured in a conventional manner to the carriage 45, withthe DC motor operating in response to control signals received from thecontroller 40 to incrementally advance the carriage 45 along guide rod44 in response to rotation of the DC motor. To provide carriagepositional feedback information to printer controller 40, a conventionalencoder strip may extend along the length of the printzone 25 and overthe service station area 48, with a conventional optical encoder readerbeing mounted on the back surface of printhead carriage 45 to readpositional information provided by the encoder strip. The manner ofproviding positional feedback information via an encoder strip readermay be accomplished in a variety of different ways known to thoseskilled in the art.

In the printzone 25, the media sheet 34 receives ink from an inkjetcartridge, such as a black ink cartridge 50 and three monochrome colorink cartridges 52, 54 and 56, shown schematically in FIG. 2. Thecartridges 50-56 are also often called “pens” by those in the art. Theblack ink pen 50 is illustrated herein as containing a pigment-basedink. While the illustrated color pens 52-56 may contain pigment-basedinks, for the purposes of illustration, color pens 52-56 are describedas each containing a dye-based ink of the colors cyan, magenta andyellow, respectively. It is apparent that other types of inks may alsobe used in pens 50-56, such as paraffin-based inks, as well as hybrid orcomposite inks having both dye and pigment characteristics.

The illustrated pens 50-56 each include small reservoirs for storing asupply of ink in what is known as an “off-axis” ink delivery system,which is in contrast to a replaceable cartridge system where each penhas a reservoir that carries the entire ink supply as the printheadreciprocates over the printzone 25 along the scan axis 46. Hence, thereplaceable cartridge system may be considered as an “on-axis” system,whereas systems which store the main ink supply at a stationary locationremote from the printzone scanning axis are called “off-axis” systems.In the illustrated off-axis printer 20, ink of each color for eachprinthead is delivered via a conduit or tubing system 58 from a group ofmain stationary reservoirs 60, 62, 64 and 66 to the on-board reservoirsof pens 50, 52, 54 and 56, respectively. The stationary or mainreservoirs 60-66 are replaceable ink supplies stored in a receptacle 68supported by the printer chassis 22. Each of pens 50, 52, 54 and 56 haveprintheads 70, 72, 74 and 76, respectively, which selectively eject inkto from an image on a sheet of media in the printzone 25. The conceptsdisclosed herein for cleaning the printheads 70-76 apply equally to thetotally replaceable inkjet cartridges, as well as to the illustratedoff-axis semi-permanent or permanent printheads, although the greatestbenefits of the illustrated system may be realized in an off-axis systemwhere extended printhead life is particularly desirable.

The printheads 70, 72, 74 and 76 each have an orifice plate with aplurality of nozzles formed therethrough in a manner well known to thoseskilled in the art. The nozzles of each printhead 70-76 are typicallyformed in at least one, but typically two linear arrays along theorifice plate. Thus, the term “linear” as used herein may be interpretedas “nearly linear” or substantially linear, and may include nozzlearrangements slightly offset from one another, for example, in a zigzagarrangement. Each linear array is typically aligned in a longitudinaldirection perpendicular to the scanning axis 46, with the length of eacharray determining the maximum image swath for a single pass of theprinthead. The illustrated printheads 70-76 are thermal inkjetprintheads, although other types of printheads may be used, such aspiezoelectric printheads. The thermal printheads 70-76 typically includea plurality of resistors which are associated with the nozzles. Uponenergizing a selected resistor, a bubble of gas is formed which ejects adroplet of ink from the nozzle and onto a sheet of paper in theprintzone 25 under the nozzle. The printhead resistors are selectivelyenergized in response to firing command control signals delivered by amulti-conductor strip 78 from the controller 40 to the printheadcarriage 45.

High Deflection

Capping System

FIGS. 2 and 3 illustrate one form of a high deflection capping system 80constructed in accordance with the present invention for sealing theprintheads 70-76 of pens 50-56. In the illustrated embodiment, thecapping system 80 includes a flexible frame 82 that has an outer borderportion 83 which is received within a pair of slots 84 of a capping sledportion 85. To secure the frame 82 to the sled 85, two fasteners, suchas rivets or self-tapping screws 86, are inserted into a pair of holes(not shown) in sled 85, with the fasteners also engaging a pair of holes87 defined by the frame border 83. While a screw and slot arrangement isshown to attach the frame 82 to sled 85, it is apparent that a varietyof other attachment means may be used to secure the frame 82 to thesled. For example, rather than sliding the frame 82 into slots 84, eachslot 84 may be closed at each end, and the frame 82 flexed for insertioninto the slots 84.

The flexible frame 82 may be constructed of any type of plastic ormetallic material having a spring characteristic that allows the frameto return to its natural, preferably flat, state after being stressed orbent into a position away from that natural state. The preferredmaterial for the frame 82 is a stainless steel, such as ASTM 301 or 304stainless steel, preferably full-hard and cold-rolled which provides asubstantially constant spring-rate over the life of the frame 82, or aprecipitation hardening steel alloy like type 17-7 typically used tomake springs and structural components. For instance, a frame 82constructed of a metallic shim stock material, on the order of 0.508millimeters (nominally 0.020 inches) thick, was found to performsuitably. A stainless steel is preferred because it has superiordurability and resistance to corrosion, not only from the ink but alsofrom other environmental factors, such as high humidity or rapid changesin temperature during transport. In addition to the 300-series stainlesssteel alloys, it is also believed that other alloys would be suitable,for example the 400-series of stainless alloys.

Conventional spring steels may also be suitable for frame 82, althoughthey may need some surface preparation, such as a paint or other coatingto protect them from corrosion due to environmental factors or fromdegradation caused by the ink itself. While various plastic materialswere not tested, it is believed that plastics may also serve as suitablematerials for the flexible frame 82. However, given the performancecharacteristics of the current commercially available plastics, metalsare preferred because these plastics have a tendency to creep whenstressed. “Creep” is a term used in the plastics industry to describethe failure of a plastic to return to its original shape after beingstressed without losing any restoring force or spring rate. The metalsproposed herein for frame 82 do not suffer creep failure. Moreover,preferably onsert molding techniques are used to manufacture cappingassembly 80, and the use of a metal frame 82 allows for higher onsertmolding temperatures. Such higher onsert molding temperatures arebelieved to promote better bonding of elastomers to the frame 82, aswell as more complete curing or cross-linking of the elastomericmaterial. Higher molding temperatures also yield faster curing times,which in turn provides a shorter manufacturing cycle, with a resultinglower cost to manufacture the cap assembly 80. Indeed, if the cap sled85 is of a plastic material, the frame 82 may be insert molded as anintegral portion of the sled 85.

As described in the Background section above, the cap sled 85 may bemoved into engagement with the printheads 72-76 in a variety ofdifferent manners known to those skilled in the art. For instance, thecap sled 85 may approach the printheads 70-76 translationally,rotationally, diagonally or though any combination of these motions,depending upon the type of sled movement mechanism employed. Severaldifferent movement mechanisms and sled arrangements are shown in U.S.Pat. Nos. 4,853,717; 5,103,244; 5,115,250; 5,155,497; 5,394,178;5,440,331; and 5,455,609, all assigned to the present assignee, theHewlett-Packard Company. Indeed, in other pen support mechanisms, it maybe more practical to move the printheads 70-76 into contact with thecapping system 80, or to move both the printheads and the capping system80 together into a printhead sealing position.

As best shown in FIG. 3, inside the border 83 a series of intricatelyfashioned holes or recesses 88, 89 and 89′ have been cut through frame82 to define four cap bases 90, 92, 94 and 96 which lie under therespective printheads 70, 72, 74 and 76 during capping. At each end ofthe cap bases 90-96, the base is attached to the border 83 by asuspension spring element, such as an S-shaped spring member 98 definedby the holes 80, 89 and 89′ formed through the frame 82. The holes 80,89 and 89′ may be formed by removing material from the frame 82, forexample through laser removal techniques, etching, punching or stamping,or other methods known to those skilled in the art. The spring elements98 may take a variety of different forms, and the configurations forsprings 98 shown herein are by way of illustration only to describe theconcepts of the flexible frame support system. Thus, it is apparent thatother spring configurations may also be used to implement theseconcepts.

Preferably four elastomeric sealing lips 100, 102, 104 and 106 areonsert molded onto each of the cap bases 90, 92, 94 and 96,respectively. The manner of onsert molding the cap lips 100-106 onto thebases 90-96 may be done in a variety of different manners known to thoseskilled in the art for bonding elastomeric materials to metals orplastics. For example, the flexible frame, here frame 82, may define aseries of holes through the frame under the sealing lips 100-106 toallow the elastomer to flow through these holes, forming an anchoringpad or stitch point 107 of the elastomer along an underside 109 of theframe 82, with these stitch points 107 being shown in FIG. 2.

The material selected for the cap lips 100-106 may be any type ofresilient, non-abrasive, elastomeric material, such as nitrile rubber,elastomeric silicone, ethylene polypropylene diene monomer (EPDM), orother comparable materials known in the art, but EPDM is preferred forits economical cost and durable sealing characteristics which endurethrough a printer's lifetime. One preferred compound for the caps100-106 of FIGS. 2 and 3 comprises a flexible elastomeric matrixcontaining particles of a material harder than the matrix which allowthe particles to resist wear and prolong the useful life of the caps.These particles may be of a nonabrasive, hard polymer, such aspolyethylene. Preferably, the particles are bonded to the elastomericmatrix with a coupling agent, such as silane. A preferred softness forthe caps 100-106 in FIGS. 2 and 3 is in the durometer range of 25-45,with a more preferred value being a durometer of 35±5, as measured onthe Shore A durometer scale.

Now that the basic components of the capping system 80 have beendescribed, the basic manner of operation and method of sealingprintheads 70-76 will be discussed. To aid in explaining this operation,a Cartesian coordinate axis system, having positive XYZ coordinate axesoriented as shown in FIG. 1, will be used. Here, the positive X-axisextends to the left from the service station area 48 across theprintzone 25, parallel with the scanning axis 46. The positive Y-axis ispointing outwardly from the front of the printer 20, in the directionwhich page 34 moves onto the output wings 36 upon completion ofprinting. The positive Z-axis extends upwardly from the surface uponwhich the printer 20 rests. This coordinate axis system is also shown inseveral of the other views to aid in this discussion.

While a variety of different embodiments of the spring elements areshown herein, such as springs 98, preferably each type of suspensionspring accomplishes the function of having both cantilevercharacteristics and torsional characteristics. These cantilever andtorsional characteristics of the suspension springs allow the cap bases90-96 to flex and rotate at least a fraction of the base out of areference plane 110, which is defined by an unflexed state of the frameborder 83. This flexibility of the cap base 90 to pivot and tilt withrespect to the reference plane 110 allows the bases to function asindependent spring-suspended platforms, similar to the ability of atrampoline to flex with respect to its frame. The trampoline analogybreaks down somewhat because a trampoline platform stretches, whereasthe illustrated bases 90-96 are substantially rigid to provide firmsupport for the cap lips 100-106. It is apparent that the bases 90-96may be locally reinforced for increased stiffness without impacting thesprings 98. For instance, the bases 90-96 may be stiffened by addingribs or dimples through molding for a plastic frame, or through astamping process for a metallic frame, or by onsert molding otherstiffening materials to the base, such as a rigid plastic member.

As described further below, the upper surface of each of the caps100-106 form sealing lips which provide a substantially hermetic sealwhen engaged against the respective printheads 70-76 to define a sealingchamber or cavity between each orifice plate, lip and cap base, whichretards drying of the ink within the nozzles. The cap lips 100-106 maybe sized to surround the printhead nozzles and form a seal against theorifice plate, although in some embodiments it may be preferable to seala larger portion of the printhead, which may be easily done by varyingthe size of the sealing lips to cover a larger area of the printheads70-76. The configuration of the preferred sealing edge of cap lips whichactually contact the printheads 70-76 is described further below withrespect to FIGS. 4-5 and 7.

FIGS. 4 and 5 show an alternate high deflection capping system 115constructed in accordance with the present invention using theelastomeric cap body 100 of FIGS. 2-3, in combination with an alternatesupport frame or base 118, here molded of a plastic material suitablefor withstanding onsert molding temperatures and pressures, which may besubstituted for the metallic cap base 90. The cap 100 has an elastomericbody 120 which may be onsert molded to the metallic cap base 90 orplastic base 118. The body has an upper surface 122 projecting upwardlyto seal the printhead 70, and a lower surface 124 extending downwardlyfrom the lower surface 109 of base 118. The upper surface 122 iscontoured to form a generally rectangular shaped sealing chamber 125,defined by an opposing pair of longitudinal lips 126, 128, and anopposing pair of high deflection lateral sealing lips 130, 132. The capbody 120 also has a bottom wall 133 which extends between lips 126-132along the upper surface of the cap base 90 to line sealing chamber 125with elastomer, which advantageously avoid leaks encountered in theearlier printers at the lip/sled interface. Projecting inwardly from thebody lower surface 124 directly under lips 132, 130 are two deflectioncavities 134, 135, respectively. While it is apparent that the shapes ofthe lips 130 and 132 may be varied, in the illustrated embodiment, thesehigh deflection lips 130, 132 are symmetrical, so a discussion of theoperation of lip 130 will suffice to explain the operation of lip 132.Here, the deflection cavity 135 serves to define opposing exterior andinterior walls 136, 138 of lip 130, with the walls 136, 138 beingbridged by a sealing wall 140. The outer surface of the interior wall138 assists in defining the sealing chamber 125. Before discussing theoperation of the high deflection sealing lips 130, 132 with respect toFIG. 7, the remainder of the components of cap 100 will be described.

As mentioned in the Background section above, there are a variety ofdifferent methods for venting the sealing chamber when contacting theprintheads 70-76 with lips 100-106 to relieve pressure and preventpushing air into the orifices, which otherwise could deprime the pens.In the illustrated embodiment, each of the cap bases 90-96, 118 has avent aperture, such as hole 142, extending from the sealing chamber to alower surface 109 of the frame 82, 118. During the onsert moldingprocess, a vent throat 144 of elastomer lines the hole 142 and extendsfrom the body upper surface 122 through to the lower surface 124.Adequate venting may be provided by adjusting the size of the effectivediameter of the vent throat 144.

Preferably, the vent throat 144 extends upwardly above the bottom wall133 of the sealing cavity 125 to define an entry neck portion 145. Theneck 145 advantageously prevents minor ink leakage from the printhead70, such as during an accidental drool event, from immediately draininginto the vent throat 144. Moisture can also accumulate in the capchamber 125 as moisture trapped in the air inside the sealing chamberbegins to condense. The exterior upper periphery of the neck 145 ispreferably formed with a relatively sharp comer (when viewed in crosssection in FIG. 5) approximating 90° (neglecting draft deviationsrequired for the molding process). This sharp periphery of neck 145, incombination with the meniscus forces operating along the upper surfaceof an ink pool, serves to hold back a substantial amount of ink fromfalling into the vent throat 144.

The lower surface 124 of the cap body 120 preferably is formed with atleast two basin gripping ridges 146, 148 which resiliently grip a catchbasin 150. The catch basin 150 has a bowl portion 152 and a rim portion154 extending outwardly from the upper edge of the bowl 152. Opposingsides of the rim 154 are grasped by the gripping ridges 146, 148 to holdthe basin tightly against the lower surface 124 of the cap body 120,with the bowl 152 positioned to collect any ink escaping from thesealing cavity 125 through the vent throat 144.

While an interior portion 156 of the bowl 152 may be left empty, in theillustrated embodiment, the bowl 152 is filled with an absorbent pad 158which may be of any type of liquid absorbent material, such as of afelt, pressboard, sponge or other material, here shown as a sponge pad158. The sponge pad 158 may be shipped from the factory in a dry state,but more preferably, the sponge 158 is soaked with a hygroscopicmaterial, such as PEG (polyethylene glycols), LEG (lipponic-ethyleneglycols), DEG (diethylene glycols) or glycerine. These hygroscopicmaterials are liquid or gelatinous compounds that can absorb up to theirown weight in water. After sealing the printhead 70, any previouslyabsorbed water is released from the hygroscopic material reducing therate of evaporation required from the nozzles to humidify the sealingchamber 125 up to near a 100% relative humidity state that assists inpreventing the ink inside the printhead nozzles from drying. Eventuallythis saturated condition within the sealed cap tapers off to ambientrelative humidity, through a vent passageway, described further belowwith respect to FIGS. 9 and 10. In addition, the use of a hygroscopicmaterial in conjunction with pad 158 displaces and reduces the volume ofair that must reach the saturation point within the sealed cap. Thereduced cap volume more quickly reaches equilibrium with the diffusionrate of the vent path, leaving the nozzles in a preferred start-upstate, particularly after a short period of time in a capped state.Moreover, when using pad 158, the foam aids in handling ink leakages,such as from accidental pen drool events.

Turning to FIGS. 4-6, the plastic frame base 118 includes a base tableportion 164 which joins the cap assembly to a service station sled 165.To couple cap assembly 100 to the sled 165, the base 118 has four legs166, 167, 168 and 169 projecting downwardly from the table 164, witheach leg 166-169 terminating in a foot portion 170, as also shown inFIG. 6. Each of the feet 170 is captured by a location arm 172 portionof the sled 165, with the arms 172 in the illustrated embodimentextending outwardly from a position underneath table 164. As shown inFIGS. 4 and 6, first and second pairs of location datums 174 and 176 mayextend from table 164 to engage a pen alignment member 178, one of whichis shown schematically in FIG. 6, or to engage datums 176 and 174 on anadjacent base that supports another cap.

As shown in FIG. 5, a biasing member, such as a compression coil spring180, is used to urge the cap assembly away from the service station sled165 and into engagement with the printhead. The sled 165 defines arecessed pocket 182, located centrally under the cap assembly 100, thatreceives the lower portion of spring 180. The upper end of spring 180wraps around the catch basin bowl 152, and pushes against the lowersurface of the basin rim 154. The feet 170 of each of the frame legs166-169 are pulled upwardly under the force of spring 180 intoengagement with the lower surface of the sled location arms 172 whenuncapped. When capped, the capping force slightly compresses the spring180, allowing the legs 166-169 to move downwardly away from the servicestation sled 165.

Before leaving the description of the cap base 118, several otherfeatures that assist in facilitating the onsert molding process arenoted with respect to FIG. 7, which shows the illustrated embodiment ofthe cap base 118 before the onsert molding process has formed the capbody 120. To form the deflection cavities 134 and 135, the table 164defines two slots 184, 185 extending therethrough. To help secure theupper and lower portions of the cap body 120 to the base 164, a firstgroup of onsert mold plug holes 186 extend through the table 164 betweenthe deflection cavity slots 184, 185. Between the slots 184, 185 andadjacent outboard edges of table 164, a second group of onsert mold plugholes 187 extend through table 164. The elastomeric material of body 120flows through holes 186 and 187 during the onsert molding process.Finally, to contain the elastomeric material of body 120 at theperiphery of the base 164, upper and lower barriers or fences 188 and189 project outwardly from the respective upper and lower surfaces ofthe base, as shown in FIGS. 5 and 6.

FIG. 7 shows the black cap 100 the sealing the printhead 70 over anencapsulant bead 190 of the black ink printhead 70. To seal theprinthead, the high deflection lip 130 comprises a sealing region thathas a central portion 191 which deflects downwardly into the hollowdeflection cavity 135 to form a smiling shape when viewed in crosssection as shown in FIG. 7. The two extreme edges of this smile-shapeddeflection form a dual seal comprising two sealing bands 192 and 194along the exterior and interior edges of lip 130, bordering the centralportion 191. In the process of forming this smiling shape, the exteriorand interior walls 136, 138 may flex or bow slightly inward or outwardas the wall 140 flexes down and buckles the walls 136, 138. Indeed, theupright support provided by walls 136 and 138 assists in defining thesealing bands 192, 194. The seals 192, 194 join each other at the endsnear where lips 130 and 132 join the longitudinal lips 126 and 128.Thus, the two opposing bands 192, 194 substantially form a seal againstthe printhead in the sealing regions 130, 132 of the cap lip.

This dual seal 192, 194 may be viewed by pressing the cap 100 against aclear surface, such as a glass window pane. The dual seal featureadvantageously accommodates sealing over other surface irregularities,such as ink residue, lint or other debris, which may inadvertently clingto the orifice plate 70-76. For example, an errant lint fiber trappedunder the exterior seal 192 would have no adverse effect on theperformance of the interior seal 194. Thus, the humid environment insidethe sealing cavity 125 when capping is maintained by seal 194, despitethe presence of any leakage caused by the lint fiber under seal 192.Indeed, the encapsulant bead 190 in FIG. 7 presents no difficulty forthe lip 130, which just flexes a little more than when sealing against aflat portion of the orifice plate of the printheads.

FIG. 8 shows the bottom surface 124 of the cap body 120 with the catchbasin 150 removed to better illustrate the shape of one embodiment ofthe basin gripping ridges 146, 148. To prevent the cap 100 from forcingair into the printhead nozzles, the vent throat 144 joins the sealingcavity 125 to the basin interior 156. As shown in FIGS. 9 and 10, theupper surface of rim 154 has a trough, here shown as a spiral grooveformed therein to define a vent passageway 195 when assembled againstthe body lower surface 124. In the illustrated embodiment, the spiralvent path 195 is defined by a spiral ridge 196 that extends upwardlyfrom an upper surface 198 of the basin rim 154. The vent passageway 195extends from an entrance port at the chamber basin chamber 156 to anexit port at ambient atmosphere to provide the last portion of the ventpath from the sealing chamber 125 to atmosphere. Preferably, the venttunnel 195 has a long and narrow configuration, with a small crosssectional area to prevent undue evaporation when the printhead issealed, while also providing an air vent passageway during the initialsealing process. By varying the length of the spiral vent path 195, adesired rate of venting may be easily achieved.

Foam-Filled

Capping System

FIGS. 11-19 show an alternate form of a foam-filled capping systemconstructed in accordance with the present invention as including one ormore two-layer, foam-filled caps 200, which may be substituted for caps100-106 of the high deflection capping systems 80, 115 illustrated abovewith respect to FIGS. 2-10. As described in the Background sectionabove, sealing four closely spaced printheads, such as those of pens50-56 in printer 20, has proved quite challenging, because the caps mustnot only adequately seal each printhead 70-76, but the caps must alsoaccommodate manufacturing tolerances accumulated between pens 50-56, andthe carriage 45, as well as the tolerances contributed by the servicestation itself. These manufacturing tolerances or “stack” refers toassuming the two worst case scenarios where one unit is built with allparts having the minimum allowable dimensions, and another unit is builtwith all parts having the maximum allowable dimensions, with the capsbeing required to seal each of these worst case extremes, where anadequate seal must be maintained on the “minimum dimension” unit, andexcess capping forces must be avoided on the “maximum dimension” unit.

The first capping solution used the torsional, flexible frame 82 asillustrated with respect to FIGS. 2 and 3. An alternate proposed systemused the cap base 118, an unfilled basin 150, and spring 180, along witha solid elastomer cap, differing from the high deflection cap 120 by nothaving deflection cavities 134, 135. The high deflection cappingassembly 115 of FIGS. 4-10 has a variety of advantages noted herein, yetthe search continued for a new a manner of reducing the capping forces,while still applying an adequate printhead seal and accommodatingmanufacturing tolerance stack. In response to this quest for a flexiblecapping system, capable of balancing and achieving these goals, thefoam-filled cap 200 was conceived. The foam-filled cap 200 may beconstructed using principles similar to those illustrated with FIGS. 2and 3, using a single frame to support plural caps 200, or usingseparate bases 118 for each cap, as described with respect to FIGS.4-10.

An intermediary cap design was proposed using a one-step foaming processto produce the cap. In this process, an elastomer material was foamedupon introduction into a mold, with the elastomer forming a skin at thesurface of the mold. Unfortunately, the caps formed by this one-stepfoaming process often had porosity at the skin, so these caps failed toproduce a reliable seal at the printheads. Furthermore, in this one-stepfoaming process, it was very difficult to control the porosity of thefoam behind the skin, particularly when the attention of themanufacturing process was directed toward forming the skin. Thus, inthis one-step foam process, there was virtually no ability to vary thewall thickness of the skin, or to otherwise customize the nature of theskin, without also effecting the material properties of the foam.Finally, the major disadvantage of caps formed using this one-stepfoaming process is the lack of manufacturing consistency from part topart, leading to a high scrap out rate as parts failed to meet qualitystandards, which then led to an ultimate higher price of those partswhich did pass quality standards.

The foam cap 200 may be manufactured as described further below for usewith a unitary flexible frame structure 82 of FIGS. 2-3, or with theframe base 218, using the venting schemes described with respect toFIGS. 4-10. The foam-filled cap 200 is a two-layer structure, with onelayer being an elastomeric skin 215 formed to define an interior cavity216, which is filled with a second layer comprising a foamed elastomernetwork or core 220. Preferably, this skin 215 and the foam core 220 areboth formed of the same materials as described above for caps 100-106,and preferably of an EPDM elastomer, with the skin hardened to adurometer of 25 to 80 or higher on the Shore A scale, or preferablybetween a range of 30-50, or even more preferably between a range of35-45, on the Shore A scale.

In the past, cap durometer selection was a very tight design criteria,limited to a small range, which in turn unfortunately limited theselection of different types of materials that could be used to form theearlier caps discussed in the Background section above. The propertiesof the thin skin 215 does not appreciably effect the overall defectionof the composite cap 200, which advantageously allows many differenttypes of materials or compounds to be used for the thin skin material.Using the foam material for core 220 no longer requires that the skinmaterial have a certain durometer for effective sealing because now, themodulus of elasticity for the composite cap 200 is a design parametercontrolled primarily by the density of the foam core 220, rather thansolely an inherent property controlled by the skin material. For theillustrated off-axis inkjet printheads 70-76, one desired range ofdeflection for the composite cap 200 would be about 0.5 mm (millimeters)deflection per 450-800 grams (about 1.0-1.5 pounds) of force.Additionally, the thin skin 215 isolates the foam core 220 from contactwith any ink residue from the printheads, which advantageously allowsthe use of materials which otherwise may not be compatible with inkjetinks, such as flouroelastomers, silicone, urethanes, etc.

The exterior portions of the foam-filled cap 200 are similar to thosedescribed above with respect to cap 100, best shown in FIGS. 4 and 5.For instance, the skin 215 has an upper surface 222 which projectsupwardly to seal around the printhead 70. The cap 200 also has a lowersurface 224 formed by portions of both skin 215 and the foam core 220,with this lower surface 224 contacting the upper surface of the framebases 82, 218. The skin upper exterior surface 222 is contoured todefine a generally rectangular shaped sealing chamber 225, defined by anopposing pair of longitudinal sealing lips 226, 228 and an opposing pairof lateral sealing lips 230, 232. Each of the exterior surfacecomponents 222-232 seal the orifice plate surrounding the nozzles ofprinthead 70, as described above for components 122-132, respectively,of the high deflection cap 100. The skin 215 defines a vent hole 234therethrough, which may be constructed to be flush with a bottom surfaceof the sealing cavity 225, or preferably, the vent hole 234 issurrounded by an optional entry neck portion 235, which may configuredas described above for neck 145 shown in FIGS. 4-5 to achieve the sameadvantages previously noted, such as to retain ink within the sealingchamber 225. In illustrated cap 200, the foam core 220 extendsunderneath each of the longitudinal side walls 226, 228, as well asunderneath the lateral walls 230, 232.

FIG. 12 illustrates one manner of constructing the foam-filled cap 200,with subparts A, B, C and D illustrating different steps in themanufacturing molding process, with the cap 200 being formed upside downwith respect to the view of FIG. 11. In step A of FIG. 12, the skin 215′is shown being formed between a lower mold cavity or die 236 and anupper mold cavity or die 238, here, with the skin 215′ not having theoptional neck 235 surrounding the vent opening 234, but with minormodification to dies 236, 238, it is apparent that such a neck could beformed in step A (e.g. see FIG. 13A). The skin 215, 215′ may be formedusing a variety of different techniques known to those skilled in theart, such as injection molding, thermoplastic injection molding methodsusing thermoplastic elastomer materials (TPEs), traditional thermosetmolding methods using thermosetting elastomer materials, liquidinjection molding (LIM) of thermoset silicone LIM materials, transfermolding, compression molding, etc.

Thus, step A of FIG. 12 shows the first layer of cap 200 as being formedto create skin 215′. To form the foam core 220 behind the sealing lipsof skin 215, a foam preform 240 may be die-cut from a sheet of foam, orseparately molded preferably into the shape shown in step B. While stepsA, C and D in FIG. 12 illustrate the construction of a single foam cap200, one preferred manner of constructing cap 200 is to form multiplecaps, such as all four caps 100, 102, 104 and 106 (also see FIG. 19) ina single step, which is illustrated schematically in step B where thefoam preform 240 has four foam cutouts 242, 244, 246 and 248 which maybe used to line the interior cavity 216 of caps 100, 102, 104, 106,respectively. Indeed, forming all four caps 100-106 in a single mold236, 238 advantageously provides for consistency between the caps andvirtually eliminates assembly errors, avoiding potential misalignment ofone cap with respect to another cap. As shown by the dashed linesconnecting steps B and C in FIG. 12, the preformed foam rectangle 242 isplaced within the interior of cavity 216, which was formed in step A. Asshown, the foam preform 240 is of a smaller size than the interior spacedefined by cavity 216.

After the preform 240 has been installed in cavity 216, a new upper moldor die 250 is then brought into contact with lower mold 236. Step D ofFIG. 12 comprises a foaming step, where heat is applied to the moldassembly 236, 250 to cause the foam preform 240 to expand into the foamnetwork or core 220. This expansion of the foam preform 240 into thefoam core 220 is also illustrated in steps C and D by the close stippledshading of the preform 240 in step C, and by a more sparse stippledshading in step D to show expansion of the preform 240 into the finalfoam core 220, which fills the voids within cavity 216.

While the foam core 240 may be molded, preferably the rectangles 242-248are cut from a foam sheet using a die cutting process. By linking eachof the preform rectangles 242-248 together as a web of rectangles, theentire foam preform 240 may be readily placed within the cavity 216 ofmultiple caps, in the illustrated embodiment four caps 100-106. Use ofthe preform 240 is believed to provide the highest degree of uniformityand cell distribution because the flow distance required for the foam tocompletely fill cavity 216 is minimized using preform 240, as opposed toother methods which may leave voids within cavity 216. Thus, use of adie-cut preform 240 not only eases manufacturing, by providing for fewerassembly steps, but also provides a more reliable finished product forcap 200, which ultimately results in more reliable operation of printer20.

While the foam preform 240 is preferred, advances in technology andmolding methods may ultimately favor use of other manufacturingprocesses, such as an injection process, for transferring the foam 220into cavity 216. As illustrated schematically in step D of FIG. 12, analternative injection foam molding process may be accomplished usinggates, such as gates 252, 254 formed within the upper die 250, to injecta raw foam 255 into cavity 216. In such a foam injection process, moreeven flow of the foam material through the cavity 216 may be achieved byusing minimal flow lengths, provided by using multiple gates 252, 254,because the foam material immediately begins to expand as it is injectedinto the cavity. For example, for a 50% fill capacity, a volume of rawor uncured foam equal to 50% of the volume of cavity 216 is injected,with the foam then being required to flow and expand to fill theremaining portions of the cavity. Currently, this foam injection processis difficult to control, and injecting differing amounts of foam into acavity often results in differing foam densities in the final core 220.Differing foam densities may translate into non-uniform sealingproperties as the cap lips 226-232 are brought into contact with theprintheads 70-76. Uneven capping forces may lead to an inadequate seal,or if a hard spot formed in the foam, possible damage to the printheadorifice plate may occur. However, many of these concerns may beaddressed by more fully studying the relevant molding factors, such asgating geometries, or through use of multiple gating schemes.Alternatively, it is apparent to those skilled in the art that blowingagents may also be used to achieve this same foaming effect to producecore 220. Advantageously, steps A-D of FIG. 12 may be accomplished usinga single lower mold half 236 in a shuttle system which progresses thedie through different manufacturing stages, or by holding the lower die236 stationary, and moving the other dies in and out of position duringthe molding process.

The process of FIG. 12, as well as the other processes described herein,may be modified slightly to form the skin from a film sheet which linesthe cavity of the lower mold 236 prior to insertion of the foam preform240, or prior to injection of the foam 255. This film sheet skin layeris preferably of a thermally stable film selected to withstand thecuring or process cycle of the foaming step D, such as of apolyethylene, Saran®, polyvinylidene chloride, polypropylene, Teflon®,and the like. During step D, the foaming heating process bonds oradheres the foam 220 to the film skin. Alternatively, this film processmay use a thin sheet of an elastomer, such as those listed previously,and preferably using an EPDM elastomer film sheet.

FIG. 13 shows an alternate manner of manufacturing the foam-filled cap200 in accordance with the present invention. In FIG. 13, the optionalneck 235 is shown being formed by a lower mold cavity or die 256 and anupper mold cavity die 258, which are otherwise similar in constructionto dies 236 and 238 of FIG. 12. To totally line the throat 234 with theelastomer of skin 215, the lower die 256 extends completely through thethroat to meet with upper die 258. Otherwise, step A of FIG. 13 iscomparable to step A of FIG. 12. Moreover, the discussion concerning thefoam preform 240 of step B in FIG. 13 is similar to that of step B inFIG. 12.

The method of FIG. 13 differs from that of FIG. 12 in that an insert 260is installed in step C of FIG. 13. Here, we see the insert 260,preferably, of a plastic material, or of a metallic material such asdescribed above for frame 82, which fits over the molded skin 215 afterthe foam insert 240 has been installed in cavity 216. The insert 260 hasa group of knit holes 262, 264 therethrough, which serve to bond,mechanically and preferably also chemically, the insert 260 to the foamcore 220 and to the skin 215. As shown in step D of FIG. 13, a secondupper die 265 is then applied over the insert 260 and the lower die 258,after which the foam preform 242 is heated to expand and fill the voidsof cavity 216. The foam preform 242 also expands to fill the knit holes262, 264, serving to bond the insert 260 to the skin 215 via the knitholes 264, and to the foam network 220 via holes 264, at bond or knitpoints 266 shown in step D of FIG. 13.

It is apparent that rather than using the foam preform 240,alternatively the foam core 220 may be formed by injecting raw, uncuredfoam 255 in step D of FIG. 13 by modifying the upper die 265 to havegates similar to gates 252, 254 of FIG. 12, and by also using knit holes262 through insert 260 as a portion of the gating system. FIG. 14illustrates a final optional step in the process of FIG. 13, hereillustrated as step E, where a third upper mold cavity die 270 has beenplaced over knit points 266. The die 270 is fashioned to mold a backinglayer 271 and a pair of basin retaining members 146′ and 148′, which maybe of the same construction as illustrated above with respect to FIG. 5,for retaining the vent basin 150.

FIG. 15 illustrates an alternate embodiment for forming a pair of basinretaining rims 146″ and 148″, which may also be of the same constructionas illustrated above with respect to FIG. 5, for retaining the ventbasin 150. Here, FIG. 15 may be considered as a final step E followingthe step D of FIG. 12, although the view of FIG. 15 illustrates theforming of the optional neck 235 surrounding vent hole 234. In FIG. 15,die 236 of FIG. 12 has been replaced with a new lower mold cavity die272 to form neck 235. FIG. 15 also illustrates the optional concept ofmolding insert 260 into cap 200 using a non-foamed elastomer to securethe insert 260 to the structure, although it is apparent that the diesshown herein may be modified to use skin 215, 215′ to secure the insert260 in place. Following the foaming operation of step D in FIG. 13,using an upper mold cavity die 274, an elastomer backing layer 275,preferably of an EPDM elastomer as used to form skin 215, 215′, is usedto form the basin retaining rims 146″, 148″. Here, a group of knitpoints 276 of the non-foamed elastomer from layer 275 are formed throughthe knit holes 264, 266 to bond the insert 260 to the foam core 220 andto the skin 215.

By careful selection of the materials for the backing layer 275, insert260, foam 220 and the skin 215, 215′, advantageously, the final basinadhering backing layer 275 advantageously bonds the insert 260 bothchemically and mechanically to the skin layer 215 and to the foamnetwork 220. While the basin retaining members 146′, 148′, 146″, 148″are shown being formed in FIGS. 14 and 15, it is apparent to thoseskilled in the art that other vent systems may be applied to the foamfilled capping assembly 200 through mounting of the cap assembly 200with the service station frame. For example, a variety of ventingschemes are noted in the Background section above, and others are showncommercially available inkjet printing mechanisms, although in thepreferred embodiment, the vent basin 150 is used, either filled with theabsorbent material 158, or left empty.

FIG. 16 illustrates another manner of constructing the foam-filled cap200, with subparts A, B, C and D illustrating different steps in themanufacturing molding process, with the cap 200 being formed upside downwith respect to the view of FIG. 11. In step A of FIG. 16, the skin 215″is shown being formed between a lower mold cavity or die 280 and anupper mold cavity or die 282, here, with the skin 215″ not having theoptional neck 235 surrounding the vent opening 234. Indeed, In thisembodiment, a final finishing operation is preferably preformed wherethe vent hole 234 is die-cut into the cap bottom after removal from thelower mold 280. The skin 215″ may be formed using a variety of differentmolding techniques as noted above.

Step A of FIG. 12 shows the first layer of cap 200 as being formed tocreate skin 215″. Here, the inner and outer sidewalls of cavity 216′have been thickened near the base to illustrate the use of a non-uniformskin thickness, which may be varied to tailor the force deflectionproperties of the composite cap 200. To form the foam core 220 behindthe sealing lips of skin 215, a single sheet foam preform 240′ has fourfoam cap regions 242′, 244′, 246′ and 248′ which may be used to line theinterior cavity 216, 216′ of caps 100, 102, 104, 106, respectively.Indeed, several groups of cap assemblies for several different printerunits may be formed in a single mold, then separated through the samedie-cut process used to form the vent holes 234 following removal of theskin from die 280 after step D is complete. As shown by the dashed linesconnecting steps B and C in FIG. 16, the portion 242′ of the foampreform 204′ is placed along the upper surface of the die 280 over skin215″.

After the preform 240′ has been installed, a new upper mold or die 284is then brought into contact with the foam preform sheet 240′ andpressed into molding contact with lower mold 280. Step D of FIG. 16comprises a foaming step, where heat is applied to the mold assembly280, 284 to cause the foam preform 240′ to expand into the foam networkor core 220. The compression of the foam 240′ in regions 285 of step Dis illustrated by the close stippled shading, whereas the expansion intothe cavity 126′ is shown as a more sparse stippled shading in step D.Use of a single preform sheet 240′ may be preferred over the contouredpreform 240 of FIGS. 12 and 13, do to ease of forming and handling sheet240′, as compared to forming and aligning the cut web of preform 240.

Now that the alternative manners of forming the foam-filled cap 200 areunderstood, an alternative manner of installing the foam caps 200 intoprinter 20 will be described with respect to FIGS. 17 and 18, whichillustrate one preferred embodiment of a multi-cap assembly 290constructed in accordance with the present invention. As mentionedabove, to decrease the number of parts required to form a cappingassembly to seal printheads 70-76 a multiple cap single sled assembly,such as capping assembly 80 shown in FIGS. 2 and 3, is preferred overthe separate cap mounting assembly 115 shown in FIGS. 4 and 5. In FIG.17, three of a group of four foam filled caps 200 are shown as caps100′, 102′ and 104′.

The multiple cap assembly 290 may be easily formed by extending theprinciples described above with respect to FIGS. 12-16 by placing aportion of an insert 292 over the border 233. The insert 292 has severalpairs of fingers, such as fingers 294 which separate the cap adjacentregions, such as regions 100′ and 102′. The cap assembly 290 also hasfoam cores 20 for each cap which may be assembled using a unitarypreform 295, shown prior to expansion in FIG. 17, and shown afterexpansion in FIG. 18. Advantageously, the insert fingers 294 of eachpair have distal ends which are separated from one another to define apassageway therethrough for interconnecting the foam cores 220 of theadjacent caps, such as 100′ and 102′, via a link portion 296 of the foampreform 295. The insert 292 is also formed with a series of knit holes264′ therethrough, with knit points 298 being formed when skin 215′″. isinitially molded. Venting provisions may be provided underneath themultiple cap assembly 290 by forming retained by rims 146′″ and 148′″when the skin 125′″ is molded, to retain basin 150 as described above.

Now that the alternative manners of forming the foam-filled cap 200 areunderstood, an alternative manner of installing the foam caps 200 intoprinter 20 will be described with respect to FIG. 19, which illustratesanother preferred embodiment of a multi-cap assembly 300 constructed inaccordance with the present invention. As mentioned above, to decreasethe number of parts required to form a capping assembly to sealprintheads 70-76 a multiple cap single sled assembly, such as cappingassembly 80 shown in FIGS. 2 and 3, is preferred over the separate capmounting assembly 115 shown in FIGS. 4 and 5. Use of an insert 260 whichextends across a mold cavity for forming four foam-filled caps 200 toseal printheads 70-76 may be easily accomplished, for instance, usingthe flexible frame assembly 82. Unfortunately, the use of insertsincreases the cost of the molding process, and thus the cost of theultimate finished part. Thus, it may be desirable to form thefoam-filled cap 200 without insert 260 as illustrated in FIG. 12, usingthe multi-cap construction 300 of FIG. 19.

In FIG. 19, the foam filled caps 200 are formed in a group of four, hereshown as caps 100′, 102′, 104′ and 106′, to seal the printheads 70, 72,74 and 76. The multiple cap assembly 300 may be easily formed using theprinciples described above with respect to FIG. 12 by extending border233 into a border blanket 302 which is placed upon a portion of aservice station cap support platform 304. Venting provisions may beprovided underneath the multiple cap assembly 300, for instance usingbasin 150 retained by rims 146′, 148′ or 146″, 148″, which may be formedby slightly modifying dies 270, 274 to be used without insert 260 or byproviding a feature in the cap platform 304 to serve as a vent. Avariety of other venting mechanisms may also be used as noted above. Forinstance, to hold the vent basin 150 in place, a pair of retaining rims(not shown) similar to rims 146 and 148 may be molded to extend from thelower surface of the insert. To secure the cap assembly 300 to theservice station cap platform 304, preferably a hold down member 305 isused to surround a periphery 306 of the border blanket 302. The mannerof attaching the hold down member 305285 to the service station capplatform 304 may be accomplished in a variety of ways known to thoseskilled in the art, such as through the use of interlocking snap fits,or by bonding as illustrated, such as with an adhesive, or usingfastener means, such as screws and the like, or using a variety of otherknown attachment schemes.

Conclusion

A variety of advantages are realized using the capping systems 100, 160and 200, such as the ability to easily mold the cap body 120. Theelimination of the multiple ridge lip concept used in the earlierdesigns provides a cap that is easier to mold, and indeed, may beeconomically manufactured by a variety of vendors. This design thenallows the printer manufacturer to obtain viable part price quotationsfrom more vendors, to obtain a better cap price, a savings which maythen be passed on to the consumer. The multiple ridged lips occasionallyhad problems with debris becoming trapped between the ridges, with aresulting decline in sealing performance, a problem which advantageouslydisappears when using the capping systems 100, 160 and 200

Besides leakage control, discussed above, a further advantage ofconstructing the chamber 125 with a continues elastomeric body is theprevention of unwanted leakage between the elastomer lips and the capsupport, as experienced in the earlier models discussed in theBackground section above. The earlier printers had to use higher cappingforces to not only seal the lips at the printhead, but also to seal thelip/sled interface where the support sled formed a portion of thesealing cavity. Indeed, the illustrated hollow cavity cap 100 only needsa capping force on the order of 75% of that required by these earlierprinters to adequately seal the printhead. Thus, there is no need toover-design both the printhead and the cap support structure to seal theprinthead using caps 100-106. Furthermore, by using onsert moldingtechniques, the cap is permanently referenced relative to the supportframe and the pen alignment datums on the frame, within much tightertolerances as opposed to earlier cap designs that used a separate caplip expanded to fit over a carrier. These earlier designs unfortunatelyoften slipped from their positions on the carrier, twisting or turningrelative to the carrier frame leaving some nozzles uncapped. Use of thestitch points 107 and the associated onsert molding techniques, inaddition to the deflection cavities 134, 135 produces a reliable,efficient and cost effective capping system.

Use of the catch basin 150, particularly when filled with thehygroscopic material soaked pad 158, advantageously handles ink spillsand moisture accumulation while maintaining a humidified environmentwhen the printhead is sealed. The capillary vent path provided by therim portion of the catch basin, as shown in FIGS. 9 and 10, preventsdepriming the nozzles as sealing is initiated. Furthermore, use of thegripping ridges, such as 146 and 147, formed along the lower surface 124of the cap body 120 aids in easily assembling the basin 150 to the capbody, particularly when using automated techniques to construct theembodiment of system 160.

A further advantage of the cap body 120 is the ability to adapt thedesign to a variety of different support structures, such as themetallic flexible frame 82 and the plastic frame 118. As discussed atlength above with respect to FIG. 7, the high deflection lips 130, 132are capable of providing a superior seal, not only over a relativelyflat portion of a printhead, but also over significant surfaceirregularities, such as the encapsulant bead 190. In making these seals,the central portion of the lips 130, 132 deflects downwardly into thedeflection cavities 135, 134, forming a smiling shape when viewed incross section as shown in FIG. 7. The two extreme edges of thissmile-shaped deflection form a dual seal 192, 194 along the interior andexterior edges of the lips 130, 132. Thus, the sealing capabilities ofthe earlier multiple ridged cap lips is achieved using the cappingsystems 100, 160 and 200, while avoiding the pitfalls of those earlierdesigns, to provide consumers with a more reliable, robust andeconomical printing unit 20.

A variety of advantages are also realized using the foam-filled cap 200,whether constructed as a single cap and mounted on a base unit 118, oras a multi-cap assembly 300 shown in FIG. 19, or one assembled on aflexible frame 82, as shown in FIGS. 2 and 3. One advantage of thefoam-filled cap assembly 200 is its enhanced performance capabilitiesover a solid elastomer cap. Separately forming the skin 215, 215′ andthen filling the cavity 216 with foam core 220 to provide a two-layerstructure advantageously provides a consistent non-porous sealingsurface at lips 226-232, which was not possible using a one-step foamingprocess, as described above. Additionally, the foam-filled cap 200advantageously seals over surface irregularities, such as encapsulantbead 190 with edges 192′, 194′ of sealing surface 191′ of lips 226-232in the manner as described above with respect to FIG. 7, which alsoavoids the molding problems associated with the earlier multiple lipdesigns, described above.

Furthermore, by separately molding the skin 215, 215′, followed by theseparate process of forming the foam core 220, both skin 215, 215′ andcore 220 may be independently optimized to enhance the sealing abilityof cap 220. For instance, the thickness of the skin may be varied toaccomplish different sealing objectives, for instance, by having athinner wall at the lateral regions 230, 232 which have to seal overencapsulant beads 190, and perhaps a thicker wall for the lateral walls226, 228 which seal along a relatively longer portion of the printheads70-76. One main advantage of the foam-filled cap 200 is the ability toprovide an adequate seal over a broad range of manufacturing tolerances,while reducing the capping forces experienced by printheads 70-76 overthat of previous capping systems. This superior seal is achieved by theability of cap 200 to be compressed to accommodate various manufacturingtolerances between the pens 50-56, carriage 45, and the service stationitself, while also being compliant enough to seal the printheads.

As a further advantage, by selecting the skin 215, 215′ and the foamcore 220 to be of the same material, during the foaming process of stepD in FIGS. 12 and 13, the foam core may molecularly bond with the skinto form a unitary structure. Moreover, during the process of molding ininsert 260, the material of foam core 220 or layer 275 may be selectedto not only physically bond at the knit points 266, but also tochemically bond with the insert 260.

One key aspect of the two-layer foam cap 200 is its composite nature. Asa composite, both the skin and the foam core 220 may be modified anddesigned to enable capabilities of a cap that are not available if onlya single element is used to produce a cap. For example, the materialthat seals against the orifice plate has certain sealing, and inkcompatibility requirements. In the past, a solid EPDM elastomer cap wasused because of its ability to seal and resist ink attack. As therequirements of the cap increase in terms of sealing performance, inkcompatibility, and force/deflection performance, a single materialsolution for a cap is limited in its ability to meet all of thesecompeting requirements. The main problem encountered with the earliersolid elastomer caps was meeting the increasing force/deflectiondemands. As mentioned in the Background section above, a foam capproduced in a single step, rather than the skin first followed by foamprocess of FIGS. 11-19, failed to meet the performance requirements andthe process lacked consistency; however it is apparent that furtherenhancements to the molding processes may be developed in the future tothe point where a one step process may be used to manufacture a suitablefoam cap 200 having the features described herein.

The ability to separately form the solid skin and the foam core of cap200 provides nearly infinite design flexibility to meet sealing, inkcompatibility, and force/deflection requirements. For instance, varyingthe wall thickness of the skin, as shown in FIG. 16, meets sealing andforce deflection goals by fine tuning the air and vapor transmissionrates through the skin, while also providing design freedom in terms ofhow the cap seals against the orifice plate of the pen. For example, thecap lips 226, 228, 203 and 232 may be formed to have thicker areas atthe inner and outer edges and thinner areas in the center, to enhancethe “smiling feature” shown in FIG. 7 for increased seal performance.Furthermore, the force deflection of the cap 200 may be altered by usingvarying thickness in different areas of the skin. Additionally, theprocesses for forming both the skin and the core may be individuallyoptimized since they are formed in two different molding steps, leadingto an optimal design for the composite foam-filled cap 200.

As mentioned above, use of a multiple cap assembly 300, or when severalcaps 200 are implemented on flexible frame 82, advantageously decreasesthe number of parts required to assemble the service station, and thusto assemble printer 20. Fewer parts advantageously reduces the assemblycosts, while also reducing related costs such as fewer parts to beordered, inventoried, and tracked. Additionally, if future designsrequire study of different cap deflection properties, modifications tothe illustrated design of cap 200 may be easily made, such as changes tothe skin material, durometer, geometry, or other variables, and thesechanges may be made independent of such changes to the foam core 220.Thus, the foam filled cap 200 has a design flexibility not previouslypossible using the earlier proposed one-step foamed cap. Additionally,by providing separate design control over the skin 215, 215′ and overthe foam core 220, other factors may also be adjusted, such as toenhance the compression-set performance of the material. Thus, use ofthe foam-filled cap 200 advantageously allows design flexibility,enhanced performance capability, and fewer parts to inventory and track,leading to fewer assembly steps to manufacture the inkjet printer 20,all of which lead to a more economical and reliable inkjet printer unitfor consumers.

We claim:
 1. A cap for sealing ink-ejecting nozzles of an inkjetprinthead in an inkjet printing mechanism, comprising: a flexible skinlayer having an exterior surface and an interior surface, with theexterior surface defining a sealing lip to surround the ink-ejectingnozzles when said cap is in a sealing position and to define a sealingchamber, with the interior surface of the skin layer defining a cavityunder at least a portion of the sealing lip; and a foam core within thecavity.
 2. A cap according to claim 1, further including an insertsandwiching the foam core between the skin layer and the insert.
 3. Acap according to claim 2 wherein the insert is of a substantially rigidmaterial.
 4. A cap according to claim 3 wherein the insert is of aplastic material.
 5. A cap according to claim 2 wherein the insert has aplurality of knit holes therethrough, and the insert is mechanicallybonded to at least one of the foam core and the skin layer at said knitholes.
 6. A cap according to claim 2 wherein the insert is chemicallybonded to at least one of the foam core and the skin layer.
 7. A capaccording to claim 2 wherein: the insert has a plurality of knit holestherethrough; the insert is mechanically bonded to at least one of thefoam core and the skin layer at said knit holes; and the insert ischemically bonded to at least one of the foam core and the skin layer.8. A cap according to claim 2 wherein the insert is bonded by a portionof the foam core to sandwich the foam core between the skin layer andthe insert.
 9. A cap according to claim 8 wherein the insert has aplurality of knit holes therethrough and said portion of the foam coreextends through said knit holes.
 10. A cap according to claim 8 furtherincluding: the skin layer defining a vent hole therethrough from theexterior surface to the interior surface; the cap further includes avent member adjacent the interior surface of the skin layer at the venthole and in fluid communication therewith; and a backing layer of anelastomer supported by said portion of the foam core, with the backinglayer defining a vent member attachment that secures the vent memberadjacent the vent hole.
 11. A cap according to claim 10 wherein the ventmember includes a mounting rim, and vent member attachment of thebacking layer comprises a pair of gripping members that resiliently gripthe vent member mounting rim.
 12. A cap according to claim 2 wherein:the insert has a plurality of knit holes therethrough; and the capfurther includes a backing layer of an elastomer sandwiching the insertbetween said backing layer and the foam core, with a portion of thebacking layer extending through said knit holes to bond the insert to atleast one of the foam core and the skin layer.
 13. A cap according toclaim 12 further including: the skin layer, insert and backing layertogether define a vent hole therethrough from the sealing chamber; thecap further includes a vent member having a mounting rim, with the ventmember in fluid communication with the vent hole; and a vent memberattachment defined by another portion of the backing layer toresiliently grip the vent member mounting rim to secure the vent memberadjacent the vent hole.
 14. A cap according to claim 1 wherein the skinlayer defines a vent hole therethrough from the exterior surface to theinterior surface, with the skin layer also defining a neck surroundingthe vent hole and projecting from the exterior surface into the sealingchamber.
 15. A cap according to claim 1 further including: a backinglayer of an elastomer sandwiching the foam core between the skin layerand said backing layer; the skin layer and backing layer togetherdefining a vent hole therethrough in fluid communication with thesealing chamber; a vent member having a mounting portion, with the ventmember in fluid communication with the vent hole; and a vent memberattachment defined by a portion of the backing layer to resiliently gripthe vent member mounting portion to secure the vent member adjacent thevent hole.
 16. A cap according to claim 1 wherein the cavity extendstotally under the sealing lip to surround the sealing chamber, with thecavity filled throughout with the foam core.
 17. A cap according toclaim 1 wherein: the skin layer is of an elastomer; and the foam core isof a foamed elastomer of the same type of elastomer as the skin layer.18. A cap according to claim 1 wherein the skin layer extends around aperiphery of the sealing lip to define a border portion, and the capfurther includes a border member overlying the border portion of theskin layer to serve as a mounting member to secure the cap to a servicestation cap platform.
 19. A cap according to claim 1 wherein the lip hasa sealing region that is substantially planar before sealing theprinthead, with the sealing region overlaying the foam core and having acentral portion bordered by two opposing bands, and with the centralportion of the sealing region deflecting into and compressing the foamcore when in the sealing position so the two opposing bandssubstantially form a seal against the printhead in the sealing region ofthe lip.
 20. A cap according to claim 1 wherein the flexible skin layeris of an elastomeric material.
 21. A cap according to claim 1 whereinthe flexible skin layer is formed of a film sheet.
 22. A cap accordingto claim 21 wherein the film sheet is of an elastomeric material.
 23. Acap according to claim 21 wherein the film sheet is of a materialselected from the group consisting of polyethylene, Saran®,polyvinylidene chloride, polypropylene, and Teflon®.
 24. A method ofconstructing a printhead cap for sealing ink-ejecting nozzles of aninkjet printhead in an inkjet printing mechanism, comprising the stepsof: molding a flexible skin layer having an exterior surface and aninterior surface, with the exterior surface defining a sealing lip tosurround the ink-ejecting nozzles when said cap is in a sealing positionand to define a sealing chamber, with the interior surface of the skinlayer defining a cavity opposite at least a portion of the sealing lip;and foaming an elastomer within the cavity to form a foam core therein.25. A method according to claim 24, wherein the foaming step comprisesinjecting a raw elastomer foam into the cavity, then expanding the rawelastomer foam to substantially fill the cavity.
 26. A method accordingto claim 24, wherein the foaming step comprises installing a foampreform over the skin layer, then expanding the foam preform tosubstantially fill the cavity with the foam core.
 27. A method accordingto claim 26 further including the step of, prior to the installing step,cutting the foam preform from a sheet of foam material into a shapewhich fits into the cavity, and wherein the installing step comprisesplacing the cut foam preform into the cavity.
 28. A method according toclaim 26, wherein the expanding step comprises the step of heating thefoam preform.
 29. A method according to claim 24 further including thestep of molding an insert to at least one of the foam core and the skinlayer.
 30. A method according to claim 29 wherein: the insert definesplural holes therethrough; and the foaming step comprises injecting araw elastomer foam into the cavity through at least one of the pluralholes through the insert, then expanding the raw elastomer foam tosubstantially fill the cavity and permeate through said plural holes ofthe insert to accomplish said step of molding the insert.
 31. A methodaccording to claim 30 further including the step of molding a backinglayer of an elastomer to bond with a portion of the elastomer whichpermeated said plural holes of the insert.
 32. A method according toclaim 29 wherein: the insert defines plural holes therethrough; and themethod further includes the step of molding a backing layer of anelastomer to sandwich the insert between the backing layer and the foamcore, with a portion of the backing layer elastomer permeating throughsaid plural holes of the insert to bond with at least one of the skinlayer and the foam core to accomplish said step of molding the insert.33. A method according to claim 32 wherein: the skin layer, insert andbacking layer are molded together to define a vent hole therethrough influid communication with the sealing chamber; and step of molding thebacking layer includes the step of molding a vent member attachment witha portion of the backing layer elastomer to resiliently grip a ventmember in a position for fluid communication with the vent hole.
 34. Amethod according to claim 29 wherein: the insert defines plural holestherethrough; and the foaming step comprises installing a foam preformin the cavity, then expanding the foam preform to substantially fill thecavity with the foam core and permeate a portion of the foam corethrough said plural holes of the insert to accomplish said step ofmolding the insert.
 35. A method according to claim 34 further includingthe step of molding a backing layer of an elastomer to bond with aportion of the foam core which permeated said plural holes of theinsert.
 36. A printhead cap constructed according to any of the methodsof claims 24 through
 35. 37. A method according to claim 24, wherein themolding step comprises molding the flexible skin layer of an elastomericmaterial.
 38. A method according to claim 24, wherein the molding stepcomprises placing a film sheet in a mold.
 39. A method according toclaim 38, wherein the placing step comprises placing a film sheet of anelastomeric material in the mold.
 40. A method according to claim 38,wherein the film sheet of the placing step is of a material selectedfrom the group consisting of polyethylene, Saran®, polyvinylidenechloride, polypropylene, and Teflon®.
 41. An inkjet printing mechanism,comprising: an inkjet printhead having ink-ejecting nozzles; a carriagethat reciprocates the printhead through a printzone for printing and toa servicing region for printhead servicing; and a capping system in theservicing region for sealing the printhead nozzles during periods ofinactivity, with the capping system including a cap support platformmoveable to a sealing position, and a printhead cap supported by the capsupport platform, with the printhead cap comprising: a flexible skinlayer having an exterior surface and a interior surface, with theexterior surface defining a sealing lip to surround the ink-ejectingnozzles when in the sealing position and to define a sealing chamber,with the interior surface of the skin layer defining a cavity under atleast a portion of the sealing lip; and a foam core within the cavity.42. An inkjet printing mechanism according to claim 41 wherein the capfurther includes an insert sandwiching the foam core between the skinlayer and the insert.
 43. An inkjet printing mechanism according toclaim 42 wherein the insert has a plurality of knit holes therethrough,and the insert is mechanically bonded to at least one of the foam coreand the skin layer at said knit holes.
 44. An inkjet printing mechanismaccording to claim 42 wherein the insert is chemically bonded to atleast one of the foam core and the skin layer.
 45. An inkjet printingmechanism according to claim 42 wherein the insert is bonded by aportion of the foam core to sandwich the foam core between the skinlayer and the insert.
 46. An inkjet printing mechanism according toclaim 42 wherein: the insert has a plurality of knit holes therethrough;and the cap further includes a backing layer of an elastomer sandwichingthe insert between said backing layer and the foam core, with a portionof the backing layer extending through said knit holes to bond theinsert to at least one of the foam core and the skin layer.
 47. Aninkjet printing mechanism according to claim 41 wherein the skin layerdefines a vent hole therethrough from the exterior surface to theinterior surface, with the skin layer also defining a neck surroundingthe vent hole and projecting from the exterior surface into the sealingchamber.
 48. An inkjet printing mechanism according to claim 41 furtherincluding: a backing layer of an elastomer sandwiching the foam corebetween the skin layer and said backing layer; the skin layer andbacking layer together defining a vent hole therethrough in fluidcommunication with the sealing chamber; a vent member having a mountingportion, with the vent member in fluid communication with the vent hole;and a vent member attachment defined by a portion of the backing layerto resiliently grip the vent member mounting portion to secure the ventmember adjacent the vent hole.
 49. An inkjet printing mechanismaccording to claim 41 wherein the lip has a sealing region that issubstantially planar before sealing the printhead, with the sealingregion overlaying the foam core and having a central portion bordered bytwo opposing bands, and with the central portion of the sealing regiondeflecting into and compressing the foam core when in the sealingposition so the two opposing bands substantially form a seal against theprinthead in the sealing region of the lip.
 50. An inkjet printingmechanism according to claim 41 wherein the flexible skin layer is of anelastomeric material.
 51. An inkjet printing mechanism according toclaim 41 wherein the flexible skin layer is formed of a film sheet. 52.An inkjet printing mechanism according to claim 51 wherein the filmsheet is of an elastomeric material.
 53. An inkjet printing mechanismaccording to claim 51 wherein the film sheet is of a material selectedfrom the group consisting of polyethylene, Saran®, polyvinylidenechloride, polypropylene, and Teflon®.